It is desirable in angiographic X-ray image data acquisition to minimize the amount of X-ray dose given to a patient throughout the course of an imaging study. This can be done by reducing the X-ray energy or reducing the frame rate of the acquisition. There are applications for X-ray data that may require a portion of an acquisition to be of higher frame rate or dose than another part. Known systems vary the frame rate during an acquisition by either setting timers or using a manual switch to trigger the change. This requires the user to predict the characteristics of the acquisition before starting it, in the case of using timers, or to incur an additional mammal step, in the case of the switch. However a user may incorrectly predict the characteristics or enter incorrect settings for imaging based on a prediction. A system according to invention principles addresses these deficiencies and related problems.